This invention relates to beams that form a grid in a suspended ceiling that has drywall or plasterboard affixed to the beams by self-tapping screws.
Beams used in grids for suspended ceilings are well known. The ceilings are either of a panel type that have panels placed in grid openings, and supported by the intersecting beams, or of a drywall or plasterboard type, wherein sheets of drywall are screwed by self-tapping screws, into the beams of the grid.
The beams, which are essentially the same for both types of ceilings, are formed by folding a strip of metal longitudinally, as by continuous rolling, into an inverted T cross section, with a bulb at the top, a two-layered web extending down from the bulb, two flanges extending horizontally opposite from one another at the lower end of the web, and a face cap over the bottom of the flanges that is folded back over, and above, the edges of the flanges. The face cap in a beam for a drywall ceiling, has indentations over its surface that capture self-tapping screws to permit the screws to penetrate the face cap and the flange. The face cap functions to hold the layers of the web together, and to carry the indentations that capture the screws.
The beams for drywall suspended ceilings have been adapted from the much more popular panel ceilings by simply forming indentations in the face cap. Beams for suspended ceilings having panels do not have the indentations in the face cap as do those beams for drywall suspended ceilings.
Since, in a drywall ceiling, the self-tapping screws are inserted from below into the tee beam by the installer without being able to see the beam, placement of the screw on the tee beam face cap is not exact, and the screw, when inserted near the edge of the face cap, often pushes the face cap and flange upwardly away from the screw without penetrating the cap and flange.
The edge of the cap and flange lack the rigidity to resist the force of the screw prior to penetration, and the indentation lacks sufficient holding power to retain a captured screw tip until penetration. The resulting lack of connection between the screw and tee reduces the drywall support, and generally is undetected by the installer.
The beam of the invention has no face cap as in the prior art. The flanges themselves of the tees are indented, and the edges of the flanges are hemmed by folding the edges downwardly and inwardly. The layers of the web of the beam are desirably secured together by, for example, stitching, so that the web is not separated in the event a screw tip contacts the tee between the two layers of the web at the centerline.
The downwardly and inwardly extending hem on the edge of each flange creates a barrier that keeps the edge of the flange in contact with the screw tip when a screw is placed near the edge, so the edge cannot lift up off the screw tip. The point of the screw is captured into one of the indentations adjacent the hem where, as the screw rotates, it penetrates into and through the flange to screw the wallboard to the tee.
A further advantage of the invention over the prior art is that since there is no need for a face cap, there is a savings in metal, in addition to the superior results from having virtually all of the self-tapping screws engage the beam to support the wallboard.